High species diversity of Echinococcus spp. in wild mammals of Namibia.

An opportunistic survey for Echinococcus spp. in wild mammals was conducted in seven distinct study areas throughout Namibia, representing all major ecosystems, between 2012 and 2021. In total, 184 individually attributable faeces and 40 intestines were collected from eight species of carnivores, and 300 carcasses or organs of thirteen species of ungulates were examined for Echinococcus cysts. Nested PCR and sequencing of the mitochondrial nad1 gene led to the identification of five species of the Echinococcus granulosus sensu lato complex. Echinococcus canadensis G6/7 was found throughout Namibia at low frequency in lions, cheetahs, African wild dogs, black-backed jackals and oryx antelopes. Echinococcus equinus was present only in northern Namibia, locally at high frequency in lions, black-backed jackals and plains zebras. Echinococcus felidis was found only in one small area in the north-east of Namibia, but with high frequency in lions and warthogs. Echinococcus granulosus sensu stricto was identified only in two African wild dogs in the north-east of Namibia, and Echinococcus ortleppi occurred in central and southern Namibia in black-backed jackals and oryx antelopes. The development of fertile cysts indicated active intermediate host roles of oryx antelopes for E. canadensis and E. ortleppi, of warthogs for E. felidis, and of plains zebras for E. equinus. Our data support earlier hypotheses of exclusive or predominant wildlife life-cycles for E. felidis involving lions and warthogs, and - in Namibia - for E. equinus involving lions and/or black-backed jackals and plains zebras. Our data further support an interlink of wild and domestic transmission for E. ortleppi. A possible involvement of livestock and domestic dogs in transmission of E. canadensis G6/7 and E. granulosus s.s., the two parasite species with highest zoonotic potential, is uncertain for Namibia and needs further investigation.

Cystic echinococcosis of ruminant livestock in Namibia.

Cystic echinococcosis (CE) is widespread and locally frequent in southern Africa where it affects humans, livestock, and wild mammals. However, most data from the region are old and do not provide information on the causative Echinococcus species. For Namibian livestock only anecdotal records were available prior to this preliminary survey. Our retrospective analysis of slaughterhouse records of CE in cattle from the commercial farming area in central and southern Namibia resulted in 1.65% CE prevalence among 35,143 slaughtered cattle in the period 2015-2016. For comparison, carcasses of ruminant livestock were prospectively examined in the communal farming areas of northern Namibia, resulting in three CE cases among only 12 cattle, and no cases among nine goats. To determine the Echinococcus species affecting Namibian livestock, a total of 53 cysts were collected from all parts of the country and analysed for species and genotype by amplification and sequencing of the nad1 gene. All 50 cattle cysts (isolated from 40 cattle), both from the commercial and communal farming areas, were Echinococcus ortleppi (all fertile, and 42/50 from the lungs), while three opportunistically collected cysts from three sheep in southern Namibia were E. canadensis G7. Our data suggest that E. ortleppi is the only CE agent that is relevant for cattle infection in Namibia, and that low prevalence in the commercial farming areas contrasts with high CE burden in the northern traditional husbandry systems. The present data provide baseline information to stimulate epidemiological studies on the transmission pathways of various CE agents in livestock, wildlife, and humans in Namibia and neighbouring countries.

A sylvatic lifecycle of Echinococcus equinus in the Etosha National Park, Namibia.

Various species of Echinococcus have been described in the past from wild mammals of sub-Saharan Africa. However, it is only recently, that a few isolates have become available for molecular identification; therefore, the involvement of wildlife in the lifecycles of the various cryptic species within Echinococcus granulosus sensu lato is still only partially known. A preliminary survey was undertaken in Etosha National Park, Namibia, from August to October 2012. Faecal samples were obtained from 34 individual wild carnivores, and metacestodes were collected from carcasses of 18 culled herbivores. Single eggs and metacestode tissue were lysed and identified from sequences of the mitochondrial nad1 gene. In case of metacestodes, the cox1 gene was additionally sequenced and haplotype networks were constructed. Echinococcus equinus was found in lions (4 of 6), black-backed jackals (2 of 7) and Burchell's zebras (11 of 12). The frequency of this parasite in the absence of domestic dogs, horses and donkeys strongly indicates its transmission in a wildlife cycle. Further, a variety of sequences were obtained from eggs and cysticerci from lions, cheetahs, caracals, spotted hyenas and oryx, which most closely clustered with species of Taenia. Only 3 of them, 2 of lion and 1 of hyena origin, could be allocated to Hydatigera (=Taenia) taeniaeformis (lion), Taenia regis (lions and oryx) and Taenia cf. crocutae (spotted hyena and oryx).